Blizzard recently posted a guide on the WoW community site dedicated to explaining the way guilds level up, the way guild experience is gained, and the benefits guild groups can bring. There isn't any new information, per se, but it is nice to have it all in one place, especially the 5-man dungeon explanation about how the experience modifier works based on the number of guild members in your party.
If you just want a refresher course on guild advancement and rewards, or if you are just learning about this stuff for the first time, the Blizzard guide is a great resource. Check it out here.
World of Warcraft: Cataclysm has destroyed Azeroth as we know it; nothing is the same! In WoW Insider's Guide to Cataclysm, you can find out everything you need to know about WoW's third expansion, from leveling up a new goblin or worgen to breaking news and strategies on endgame play.